The present disclosure relates to a receiving antenna, a receiving antenna unit, and a receiving system.
In the related art, endoscopes have been widely used as a medical observation device introduced into a body of a subject such as a patient to observe the inside of the subject. In recent years, a capsule endoscope, which is a swallow-type radio wave generator having in a casing an imaging device and a communication device for wirelessly transmitting an image signal captured by the imaging device to the outside of the body, has been developed. The capsule endoscope is swallowed from a patient's mouth for observation inside the subject, and then moves along the inside of organs such as esophagus, stomach, or small intestine by peristaltic movement of the organs to sequentially capture the inside until it is naturally excreted from the subject.
While the capsule endoscope moves inside the subject, images captured by the capsule endoscope are sequentially transmitted to the outside of the body via wireless communication, and are stored in a memory provided inside or outside the receiving device via an external receiving antenna unit, or are displayed on a display provided in the receiving device. A user such as a doctor or a nurse may obtain an image stored in the memory and store it in an information processing device using a cradle into which the receiving device is inserted, and may perform observation or diagnosis based on the image displayed on the display of the information processing device or the position of the capsule endoscope at the time of capturing of the corresponding image.
However, when the radio communication described above is performed, the antenna element of the receiving antenna unit is connected to, for example, a ground serving as a ground potential on a circuit board where a radio communication circuit is mounted (for example, see JP 2006-166958 A). Therefore, it is possible to adjust directivity or an impedance characteristic of the receiving antenna by connecting the antenna element and the ground.
There is a need for a receiving antenna, a receiving antenna unit, and a receiving system capable of improving position detection accuracy of the radio wave generator.